In wireless communications, it is generally desired that the limited frequency resources be used effectively. In order to effectively utilize the frequency resources, the radio waves of the same frequency are used repeatedly as close in distance as possible, for example. In that case, the communication quality degrades due to the co-channel interference from the neighboring base station apparatuses or the like that use the same frequency. One of the techniques to prevent the degradation of communication quality due to the co-channel interference is adaptive array antenna technology. In the adaptive array antenna technology, the signals received by a plurality of antennas, respectively, are weighted with different weighting factors and then combined together.
To adaptively update the weighting factors, adaptive algorithms, such as RLS (Recursive Least Squares) algorithm and LMS (Least Mean Squares) algorithm, are used. There are also cases where the weighting factors are calculated based on the response characteristics in a channel between a transmitting side and a receiving side. Adaptive array signal processing like this is sometimes applied to a multicarrier signal such as an OFDM (Orthogonal Frequency Division Multiplexing) signal (See Patent Document 1, for instance).
[Patent Document 1] Japanese Patent Application Publication No. 2006-186421.